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I read a paper, "how hard can it be? designing and implementing a deployable multipath TCP", in the 5-th paragraph of section 3.2, it says: "if only the server is multi-homed, the wide prevalence of NATs makes it unlikely that a new SYN it sends will be received by a client"
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misteryesMay 24 '13 at 12:59

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+1 Because this is a perfectly sound question. Voting down this question is really unfair.
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artistoexMay 25 '13 at 16:08

@Ramhound Q:How on earth could the server initiate the connection and why would this be something you want? A:exactly the same way, the client initiates a connection to the server
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artistoexMay 25 '13 at 16:18

Web browsers support FTP. RFC 959, Section 3.2: The server, upon receiving the transfer request, will initiate the data connection to the [client] port. Left as an exercise to the reader: find a browser whose ftp module supports client side passive data transfer.
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artistoexMay 25 '13 at 16:21

if the browser use port 32000 to connect to web server, then web server(port 80) will initiate a data connection to the same port(32000)or other port?
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misteryesMay 26 '13 at 0:08